package com.wxtl.util;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

import org.apache.commons.lang.SystemUtils;

/**
 * 使用java.security.MessageDigest类写的一个工具类用来获取MD5码
 * @author Talen
 * @see java.security.MessageDigest
 */
public class MD5Util {
	/**  
	* 默认的密码字符串组合，apache校验下载的文件的正确性用的就是默认的这个组合  
	*/  
	protected static char hexDigits[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9','a', 'b', 'c', 'd', 'e', 'f' };   
	protected static MessageDigest messagedigest = null;   
	static{   
	   try{   
	    messagedigest = MessageDigest.getInstance("MD5");   
	   }catch(NoSuchAlgorithmException e){   
	    System.err.println(MD5Util.class.getName()+"初始化失败，MessageDigest不支持MD5Util。");   
	    e.printStackTrace();   
	   }   
	}   
	  

	/**
	     * 向getMD5方法传入一个你需要转换的原始字符串，将返回字符串的MD5码
	     * @param code 原始字符串
	     * @return 返回字符串的MD5码
	     */
//	public static String getMD5(String code) throws Exception {
//		MessageDigest messageDigest = MessageDigest.getInstance("MD5");
//		byte[] bytes = code.getBytes();
//		byte[] results = messageDigest.digest(bytes);
//		StringBuilder stringBuilder = new StringBuilder();
//
//		for (byte result : results) {
//			//将byte数组转化为16进制字符存入stringbuilder中
//			stringBuilder.append(String.format("%02x", result));
//		}
//
//		return stringBuilder.toString();
//	}
	/**  
	* 适用于上G大的文件  
	* @param file  
	* @return  
	* @throws IOException  
	*/  
	public static String getMD5String(File file) throws IOException {   
	   FileInputStream in = new FileInputStream(file);   
	   FileChannel ch = in.getChannel();   
	   MappedByteBuffer byteBuffer = ch.map(FileChannel.MapMode.READ_ONLY, 0, file.length());   
	   messagedigest.update(byteBuffer);   
	   return bufferToHex(messagedigest.digest());   
	}   
	private static String bufferToHex(byte bytes[]) {   
		return bufferToHex(bytes, 0, bytes.length);   
	}   
		  
	private static String bufferToHex(byte bytes[], int m, int n) {   
	   StringBuffer stringbuffer = new StringBuffer(2 * n);   
	   int k = m + n;   
	   for (int l = m; l < k; l++) {   
	    appendHexPair(bytes[l], stringbuffer);   
	   }   
	   return stringbuffer.toString();   
	}   
	  
	  
	private static void appendHexPair(byte bt, StringBuffer stringbuffer) {   
	   char c0 = hexDigits[(bt & 0xf0) >> 4];   
	   char c1 = hexDigits[bt & 0xf];   
	   stringbuffer.append(c0);   
	   stringbuffer.append(c1);   
	}   
	  
	public static boolean checkPassword(String password, String md5PwdStr) {   
	   String s = getMD5String(password);   
	   return s.equals(md5PwdStr);   
	}
		
	public static String getMD5String(String s) {   
	   return getMD5String(s.getBytes());   
	}   
			  
	public static String getMD5String(byte[] bytes) {   
	   messagedigest.update(bytes);   
	   return bufferToHex(messagedigest.digest());   
	}   
	
	public static void main(String[] args) {
		System.out.println(MD5Util.getMD5String("12345"+Constants.SALT));
	}

}